Proceeding from a goal proclaimed by the WHO to reduce the cancer mortality in the European region in persons not older than 65 years up to the year 2000 at least by 15%, necessary activities, concerning chemical carcinogens are discussed. Determinants of cancer risk including the main categories of chemical carcinogens are described. Special attention is called to the inhibitors of initiating processes and of promotors and antipromotors. To reduce the cancer risk substantially by elimination or reduction of individual carcinogens or risk factors only it is not to be expected. Consequently more complex activities in cancer prevention seem to be necessary concerning carcinogens, anticarcinogens, promotors and antipromotors.